.\" Copyright (C) 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
.\" Copyright (C) 2000-2002 Internet Software Consortium.
.\" 
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\" 
.\" THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
.\" REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
.\" AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
.\" INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
.\" LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
.\" OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
.\" PERFORMANCE OF THIS SOFTWARE.
.\"
.\" $ISC: host.1,v 1.14.18.14 2007/05/09 03:33:12 marka Exp $
.\"
.hy 0
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.\"     Title: host
.\"    Author: 
.\" Generator: DocBook XSL Stylesheets v1.71.1 <http://docbook.sf.net/>
.\"      Date: Jun 30, 2000
.\"    Manual: BIND9
.\"    Source: BIND9
.\"
.TH "HOST" "1" "Jun 30, 2000" "BIND9" "BIND9"
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.SH "NAME"
host \- DNS lookup utility
.SH "SYNOPSIS"
.HP 5
\fBhost\fR [\fB\-aCdlnrsTwv\fR] [\fB\-c\ \fR\fB\fIclass\fR\fR] [\fB\-N\ \fR\fB\fIndots\fR\fR] [\fB\-R\ \fR\fB\fInumber\fR\fR] [\fB\-t\ \fR\fB\fItype\fR\fR] [\fB\-W\ \fR\fB\fIwait\fR\fR] [\fB\-m\ \fR\fB\fIflag\fR\fR] [\fB\-4\fR] [\fB\-6\fR] {name} [server]
.SH "DESCRIPTION"
.PP
\fBhost\fR
is a simple utility for performing DNS lookups. It is normally used to convert names to IP addresses and vice versa. When no arguments or options are given,
\fBhost\fR
prints a short summary of its command line arguments and options.
.PP
\fIname\fR
is the domain name that is to be looked up. It can also be a dotted\-decimal IPv4 address or a colon\-delimited IPv6 address, in which case
\fBhost\fR
will by default perform a reverse lookup for that address.
\fIserver\fR
is an optional argument which is either the name or IP address of the name server that
\fBhost\fR
should query instead of the server or servers listed in
\fI/etc/resolv.conf\fR.
.PP
The
\fB\-a\fR
(all) option is equivalent to setting the
\fB\-v\fR
option and asking
\fBhost\fR
to make a query of type ANY.
.PP
When the
\fB\-C\fR
option is used,
\fBhost\fR
will attempt to display the SOA records for zone
\fIname\fR
from all the listed authoritative name servers for that zone. The list of name servers is defined by the NS records that are found for the zone.
.PP
The
\fB\-c\fR
option instructs to make a DNS query of class
\fIclass\fR. This can be used to lookup Hesiod or Chaosnet class resource records. The default class is IN (Internet).
.PP
Verbose output is generated by
\fBhost\fR
when the
\fB\-d\fR
or
\fB\-v\fR
option is used. The two options are equivalent. They have been provided for backwards compatibility. In previous versions, the
\fB\-d\fR
option switched on debugging traces and
\fB\-v\fR
enabled verbose output.
.PP
List mode is selected by the
\fB\-l\fR
option. This makes
\fBhost\fR
perform a zone transfer for zone
\fIname\fR. Transfer the zone printing out the NS, PTR and address records (A/AAAA). If combined with
\fB\-a\fR
all records will be printed.
.PP
The
\fB\-i\fR
option specifies that reverse lookups of IPv6 addresses should use the IP6.INT domain as defined in RFC1886. The default is to use IP6.ARPA.
.PP
The
\fB\-N\fR
option sets the number of dots that have to be in
\fIname\fR
for it to be considered absolute. The default value is that defined using the ndots statement in
\fI/etc/resolv.conf\fR, or 1 if no ndots statement is present. Names with fewer dots are interpreted as relative names and will be searched for in the domains listed in the
\fBsearch\fR
or
\fBdomain\fR
directive in
\fI/etc/resolv.conf\fR.
.PP
The number of UDP retries for a lookup can be changed with the
\fB\-R\fR
option.
\fInumber\fR
indicates how many times
\fBhost\fR
will repeat a query that does not get answered. The default number of retries is 1. If
\fInumber\fR
is negative or zero, the number of retries will default to 1.
.PP
Non\-recursive queries can be made via the
\fB\-r\fR
option. Setting this option clears the
\fBRD\fR
\(em recursion desired \(em bit in the query which
\fBhost\fR
makes. This should mean that the name server receiving the query will not attempt to resolve
\fIname\fR. The
\fB\-r\fR
option enables
\fBhost\fR
to mimic the behavior of a name server by making non\-recursive queries and expecting to receive answers to those queries that are usually referrals to other name servers.
.PP
By default
\fBhost\fR
uses UDP when making queries. The
\fB\-T\fR
option makes it use a TCP connection when querying the name server. TCP will be automatically selected for queries that require it, such as zone transfer (AXFR) requests.
.PP
The
\fB\-4\fR
option forces
\fBhost\fR
to only use IPv4 query transport. The
\fB\-6\fR
option forces
\fBhost\fR
to only use IPv6 query transport.
.PP
The
\fB\-t\fR
option is used to select the query type.
\fItype\fR
can be any recognized query type: CNAME, NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
\fBhost\fR
automatically selects an appropriate query type. By default it looks for A records, but if the
\fB\-C\fR
option was given, queries will be made for SOA records, and if
\fIname\fR
is a dotted\-decimal IPv4 address or colon\-delimited IPv6 address,
\fBhost\fR
will query for PTR records. If a query type of IXFR is chosen the starting serial number can be specified by appending an equal followed by the starting serial number (e.g. \-t IXFR=12345678).
.PP
The time to wait for a reply can be controlled through the
\fB\-W\fR
and
\fB\-w\fR
options. The
\fB\-W\fR
option makes
\fBhost\fR
wait for
\fIwait\fR
seconds. If
\fIwait\fR
is less than one, the wait interval is set to one second. When the
\fB\-w\fR
option is used,
\fBhost\fR
will effectively wait forever for a reply. The time to wait for a response will be set to the number of seconds given by the hardware's maximum value for an integer quantity.
.PP
The
\fB\-s\fR
option tells
\fBhost\fR
\fInot\fR
to send the query to the next nameserver if any server responds with a SERVFAIL response, which is the reverse of normal stub resolver behavior.
.PP
The
\fB\-m\fR
can be used to set the memory usage debugging flags
\fIrecord\fR,
\fIusage\fR
and
\fItrace\fR.
.SH "IDN SUPPORT"
.PP
If
\fBhost\fR
has been built with IDN (internationalized domain name) support, it can accept and display non\-ASCII domain names.
\fBhost\fR
appropriately converts character encoding of domain name before sending a request to DNS server or displaying a reply from the server. If you'd like to turn off the IDN support for some reason, defines the
\fBIDN_DISABLE\fR
environment variable. The IDN support is disabled if the variable is set when
\fBhost\fR
runs.
.SH "FILES"
.PP
\fI/etc/resolv.conf\fR
.SH "SEE ALSO"
.PP
\fBdig\fR(1),
\fBnamed\fR(8).
.SH "COPYRIGHT"
Copyright \(co 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
.br
Copyright \(co 2000\-2002 Internet Software Consortium.
.br
